SOLUBILITY RULES
1. Salts of ammonium (NH4+ 1) and Group I metal ions are always soluble.
2. a. All chlorides (Cl- 1) are soluble except AgCl, Hg2Cl2, and PbCl2 which are insoluble.
b. All bromides (Br- 1) are soluble except AgBr, Hg2Br2, HgBr2, and PbBr2 which are insoluble.
c. All iodides (I-1) are soluble except AgI, Hg2I2, HgI2, and PbI2 which are insoluble.
3. Chlorates (ClO3-1), nitrates (NO3- 1), and acetates (CH3COO- 1) are soluble.
4. Sulfates (SO4-2) are soluble except CaSO4, SrSO4, BaSO4, Hg2SO4, HgSO4, PbSO4, and Ag2SO4 which are insoluble.
5. Phosphates (PO4-3), and carbonates (CO3-2) are insoluble except
NH4+1 and Group I metal compounds.
6. All metallic oxides (O-2) are insoluble except NH4+1 and Group I metal compounds.
7. All metallic hydroxides (OH- 1) are insoluble except NH4+ 1 and Group I and Group II from calcium down.
8. All sulfides (S-2) are insoluble except NH4+ 1 and Groups I and II.
Solubility Rules
1. All compounds containing alkali metal cations and the ammonium ion are soluble.
2. All compounds containing NO3-1, ClO4-1, ClO31-, and C2H3O2-1 anions are soluble.
3. All chlorides, bromides, and iodides are soluble except those containing Ag+1, Pb2+, or Hg2+ .
4. All sulfates are soluble except those containing Hg2+,Pb2+, Sr2+, Ca2+, or Ba2+.
5. All hydroxides are insoluble except compounds of the alkali metals, Ca2+,Sr2+, and Ba2+.
6. All compounds containing PO43-, S2-, CO32-, and SO32- ions are insoluble except those that also contain alkali metals or NH4+1.
Always Always Soluble compounds with alkali metal ions
(Li+, Na+, K+, Cs+, Rb+), NH4+, NO3–, C2H3O2–, ClO3–, & ClO4–
Usually Soluble
Cl–, Br–, I– [except “AP/H”... Ag+, Pb2+, Hg22+]
SO42– [except “CBS”: Ca2+, Ba2+, Sr2+ & “PBS”: Pb2+]
Usually NOT Soluble
O2–, OH– [except alkali and “CBS” Ca2+, Ba2+, Sr2+ ]
Never Soluble
CO32–, SO32–, S2–, PO43– [except NH4+ & alkali]
NOTE: some of these insoluble compounds WILL dissolve
in acid solutions because of gas formation... useful idea!